CVE-2026-15701 in NR1800X
Summary
by MITRE • 07/14/2026
A weakness has been identified in Totolink NR1800X 9.1.0u.6279_B20210910. Affected by this issue is the function Form_Logout of the file /formLogout.htm of the component lighttpd. This manipulation of the argument Host causes stack-based buffer overflow. The attack is possible to be carried out remotely. The exploit has been made available to the public and could be used for attacks.
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Analysis
by VulDB Data Team • 07/14/2026
The vulnerability in Totolink NR1800X firmware version 9.1.0u.6279_B20210910 represents a critical stack-based buffer overflow flaw within the lighttpd web server component. This weakness specifically affects the Form_Logout function located in the /formLogout.htm file, creating a dangerous attack surface that allows remote exploitation. The vulnerability manifests when an attacker manipulates the Host header argument, which triggers improper input validation and memory handling within the affected software component. The stack-based nature of this buffer overflow means that the malicious input can overwrite adjacent memory locations on the program's stack, potentially leading to arbitrary code execution or system compromise.
The technical implementation of this vulnerability stems from inadequate bounds checking in the lighttpd web server module responsible for processing logout requests. When the Host header parameter is processed by the Form_Logout function, the software fails to properly validate the input length against the allocated buffer space, creating a condition where excessive data can overwrite stack memory. This flaw aligns with CWE-121 Stack-based Buffer Overflow, which specifically addresses buffer overflows occurring in stack memory regions. The remote exploitability of this vulnerability is particularly concerning as it allows attackers to execute malicious code without requiring physical access to the device, making it a significant threat vector for network-based attacks.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it provides attackers with potential pathways for complete system compromise. Successful exploitation could enable unauthorized users to gain administrative privileges on the router, allowing them to modify network configurations, intercept traffic, or establish persistent backdoors. The public availability of exploits for this vulnerability increases the risk profile significantly, as it removes the requirement for advanced technical skills to carry out attacks. This situation particularly affects enterprise and residential networks that rely on these devices for internet connectivity, potentially exposing large user bases to coordinated attacks.
Security mitigation strategies must address both immediate remediation and long-term defensive measures. The most effective approach involves updating the firmware to a version that includes proper input validation and buffer size enforcement for the Host header parameter. Network administrators should implement firewall rules that limit access to the affected web interface and monitor for suspicious Host header patterns in network traffic logs. Additionally, implementing intrusion detection systems can help identify exploitation attempts targeting this specific vulnerability. Organizations should also consider segmenting network access to limit potential lateral movement if an attacker successfully compromises a device. The vulnerability demonstrates the importance of regular firmware updates and proper input validation practices as outlined in the OWASP Top Ten security principles, particularly focusing on injection flaws and improper error handling that can lead to buffer overflow conditions.